Date:   Fri, 03 Mar 2017 18:45:40 +0200
From:   Laurent Pinchart <laurent.pinchart@...asonboard.com>
To:     dri-devel@...ts.freedesktop.org
Cc:     Daniel Vetter <daniel@...ll.ch>, Laura Abbott <labbott@...hat.com>,
        devel@...verdev.osuosl.org, romlem@...gle.com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        arve@...roid.com, linux-kernel@...r.kernel.org,
        linaro-mm-sig@...ts.linaro.org, linux-mm@...ck.org,
        Riley Andrews <riandrews@...roid.com>,
        Mark Brown <broonie@...nel.org>,
        Daniel Vetter <daniel.vetter@...el.com>,
        linux-arm-kernel@...ts.infradead.org, linux-media@...r.kernel.org
Subject: Re: [RFC PATCH 00/12] Ion cleanup in preparation for moving out of staging

Hi Daniel,

On Friday 03 Mar 2017 11:04:33 Daniel Vetter wrote:
> On Thu, Mar 02, 2017 at 01:44:32PM -0800, Laura Abbott wrote:
> > Hi,
> > 
> > There's been some recent discussions[1] about Ion-like frameworks. There's
> > apparently interest in just keeping Ion since it works reasonablly well.
> > This series does what should be the final clean ups for it to possibly be
> > moved out of staging.
> > 
> > This includes the following:
> > - Some general clean up and removal of features that never got a lot of
> >   use as far as I can tell.
> > 
> > - Fixing up the caching. This is the series I proposed back in December[2]
> >   but never heard any feedback on. It will certainly break existing
> >   applications that rely on the implicit caching. I'd rather make an
> >   effort to move to a model that isn't going directly against the
> >   establishement though.
> > 
> > - Fixing up the platform support. The devicetree approach was never well
> >   recieved by DT maintainers. The proposal here is to think of Ion less as
> >   specifying requirements and more of a framework for exposing memory to
> >   userspace.
> > 
> > - CMA allocations now happen without the need of a dummy device structure.
> >   This fixes a bunch of the reasons why I attempted to add devicetree
> >   support before.
> > 
> > I've had problems getting feedback in the past so if I don't hear any
> > major objections I'm going to send out with the RFC dropped to be picked
> > up. The only reason there isn't a patch to come out of staging is to
> > discuss any other changes to the ABI people might want. Once this comes
> > out of staging, I really don't want to mess with the ABI.
> > 
> > Feedback appreciated.
> 
> Imo looks all good. And I just realized that cross-checking with the TODO,
> the 2 items about _CUSTOM and _IMPORT ioctls I noted are already there.
> 
> Otherwise I looked through the patches, looks all really reasonable.

Two more items that need to be addressed in my opinion :

- Let's not export the ion_client API, we don't want drivers to be ion-
specific. Only the dma-buf interface should be visible to drivers.

- I haven't seen any proposal how a heap-based solution could be used in a 
generic distribution. This needs to be figured out before committing to any 
API/ABI.

> Wrt merging, my experience from destaging the android syncpt stuff was
> that merging the patches through the staging tree lead to lots of
> cross-tree issues with the gpu folks wanting to use that. Ion will
> probably run into similar things, so I'd propose we pull these cleanup
> patches and the eventual de-staging in throught drm. Yes that defacto
> means I'm also volunteering myself a bit :-)
> 
> In the end we could put it all into drivers/gpu/ion or something like
> that.
> 
> Thoughts? Greg?
> -Daniel
> 
> > Thanks,
> > Laura
> > 
> > [1] https://marc.info/?l=linux-kernel&m=148699712602105&w=2
> > [2] https://marc.info/?l=linaro-mm-sig&m=148176050802908&w=2
> > 
> > Laura Abbott (12):
> >   staging: android: ion: Remove dmap_cnt
> >   staging: android: ion: Remove alignment from allocation field
> >   staging: android: ion: Duplicate sg_table
> >   staging: android: ion: Call dma_map_sg for syncing and mapping
> >   staging: android: ion: Remove page faulting support
> >   staging: android: ion: Remove crufty cache support
> >   staging: android: ion: Remove old platform support
> >   cma: Store a name in the cma structure
> >   cma: Introduce cma_for_each_area
> >   staging: android: ion: Use CMA APIs directly
> >   staging: android: ion: Make Ion heaps selectable
> >   staging; android: ion: Enumerate all available heaps
> >  
> >  drivers/base/dma-contiguous.c                      |   5 +-
> >  drivers/staging/android/ion/Kconfig                |  51 ++--
> >  drivers/staging/android/ion/Makefile               |  14 +-
> >  drivers/staging/android/ion/hisilicon/Kconfig      |   5 -
> >  drivers/staging/android/ion/hisilicon/Makefile     |   1 -
> >  drivers/staging/android/ion/hisilicon/hi6220_ion.c | 113 ---------
> >  drivers/staging/android/ion/ion-ioctl.c            |   6 -
> >  drivers/staging/android/ion/ion.c                  | 282
> >  ++++++--------------- drivers/staging/android/ion/ion.h                 
> >  |   5 +-
> >  drivers/staging/android/ion/ion_carveout_heap.c    |  16 +-
> >  drivers/staging/android/ion/ion_chunk_heap.c       |  15 +-
> >  drivers/staging/android/ion/ion_cma_heap.c         | 102 ++------
> >  drivers/staging/android/ion/ion_dummy_driver.c     | 156 ------------
> >  drivers/staging/android/ion/ion_enumerate.c        |  89 +++++++
> >  drivers/staging/android/ion/ion_of.c               | 184 --------------
> >  drivers/staging/android/ion/ion_of.h               |  37 ---
> >  drivers/staging/android/ion/ion_page_pool.c        |   3 -
> >  drivers/staging/android/ion/ion_priv.h             |  57 ++++-
> >  drivers/staging/android/ion/ion_system_heap.c      |  14 +-
> >  drivers/staging/android/ion/tegra/Makefile         |   1 -
> >  drivers/staging/android/ion/tegra/tegra_ion.c      |  80 ------
> >  include/linux/cma.h                                |   6 +-
> >  mm/cma.c                                           |  25 +-
> >  mm/cma.h                                           |   1 +
> >  mm/cma_debug.c                                     |   2 +-
> >  25 files changed, 312 insertions(+), 958 deletions(-)
> >  delete mode 100644 drivers/staging/android/ion/hisilicon/Kconfig
> >  delete mode 100644 drivers/staging/android/ion/hisilicon/Makefile
> >  delete mode 100644 drivers/staging/android/ion/hisilicon/hi6220_ion.c
> >  delete mode 100644 drivers/staging/android/ion/ion_dummy_driver.c
> >  create mode 100644 drivers/staging/android/ion/ion_enumerate.c
> >  delete mode 100644 drivers/staging/android/ion/ion_of.c
> >  delete mode 100644 drivers/staging/android/ion/ion_of.h
> >  delete mode 100644 drivers/staging/android/ion/tegra/Makefile
> >  delete mode 100644 drivers/staging/android/ion/tegra/tegra_ion.c

-- 
Regards,

Laurent Pinchart

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